Rosin refining



Patented July 13, 1943 ROSIN REFINING Robert W. Martin, Wilmington, Del., assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 8, 1940, Serial No. 364,795

Claims.

This invention relates to the refining of rosin and more particularly to the refining of rosin by a dissolution process.

Rosin has been heretofore refined in various Ways such as by treatment with selective solvents, selective adsorbents and the like. These .refining processes have not been altogether satisfactory due to the difiiculty of obtaining the desired yield of rosin of the desired color grade at an economical cost of operation.

The principal object of this invention is to devise an improved process of refining rosin. Another object is to devise a process which is simpler and less expensive than processes heretofore in use. process which may advantageously be employed prior to the conventional refining process with selective solvent or selective adsorbent, whereby a higher yield of rosin of a given color grade or rosin of a paler grade may be produced. Stillother objects will more fully hereinafter appear.

I have discovered that crude or impure rosin may advantageously be decolorized by dissolving one part by weight of the rosin in from about 1 to about 10 parts by weight of a normally liquid petroleum hydrocarbon solvent comprising a preponderance of hexane, separating the undissolved or precipitated constituents from the solution, and evaporating the solvent from the solution to recover the decolorized rosin.

As the solvent, I may use any petroleum distillate comprising at least 50% by Weight, and preferably at least about 90% by weight, of hexane. The term hexane is used in a broad sense to designate any aliphatic saturated hydrocarbon having 6 carbon atoms, and mixtures of such hydrocarbons. I have obtained excellent results using commercial hexane having a boiling point range of from about 60 C. to about 70 C. and an aniline point of 64.8 C. Preferably, any components of the solvent other than hexane are the closely allied paraffin hydrocarbons, pentane and heptane. However, in view of the poorer refining results which are imparted by heptane in substantial proportions, it is preferred to use a solvent containing less than about 5% by weight of heptane. The use of a solvent comprising principally hexane with small amounts of pentane is permissible provided the initial boiling point of the solvent is not below about 33 C. Preferably, the content of pentane .does not exceed about by weight of the solvent. The solvent preferably has an end boiling point not above about 100 C.

The proportions of crude rosin and solvent Still another object is to devise a employed may vary within the limits indicated above, the particular proportions selected depending upon the amount of color bodies present in the impure rosin being treated, the particular conditions of treatment, etc. A preferred proportion is one part of the impure rosin to about nine parts of solvent in the case where the crude resinous extract derived from pine wood by extraction With benzene is being treated.

It is preferred to employ a petroleum hydrocarbon solvent containing minimum amounts of non-paraffin hydrocarbons such as aromatic, naphthenic, or unsaturated hydrocarbons. Thus, it is preferred to use a solvent such as commercial hexane, containing less than 3% of unsaturates, less than 3% of aromatics, and less than 15% of naphthenes, the total of these nonparafiins being less than 15%. For example, I have obtained excellent results using commercial hexane containing no measurable amount of unsaturates, 217% of aromatics, and 10% of naphthenes, the analytical content of paraffins being 87%. While the presence of these undesirable components may be determined by conventional analytical methods, a convenient method of determining approximately the suitability of a given hexane is by the determination of the aniline point. It is preferred to employ a solvent having an aniline point above C. The aniline point of the commercial hexane, the analysis of which was just given 64.8" C.

Instead of commercial hexane, other petroleum hydrocarbons may be employed such as for example low boiling gasoline, or petroleum ether; or similar low boiling liquid petroleum distillate which is substantially saturated and substantially free from aromatic compounds.

The rosin to be purified in accordance with the present invention may be any dark-colored rosin. The invention gives more marked decolorization when extremely-dark grades of rosin are treated thereby. For example, the crude total resinous extract obtained from deciduous pine wood by means of an aromatic solvent such as benzene or toluene may conveniently be decolorized and markedly refined by the process of the present invention. For example, the process of the present invention when applied to such a crude total resinous extract from pine wood is readily capable of yielding rosin of a color grade as high as H or even as high as I, whereas the rosin contained in the crude rosin referred to and separated by conventional methods grades FF or lower.

The procedure in accordance with the present into practice.

invention may comprise heating the solution of crude rosin in the solvent to an elevated temperature as for example to the refluxing temperature, followed by cooling to room temperature or below, say to at least about C., filtering the mixture or decanting the clear rosin solution from the precipitate or undissolved resinous material, and recovering the rosin from the solution as for example by evaporation or distillation of the solvent therefrom. A preferred procedure is to carry out the dissolution at not above about 35 C. and to maintain the mixture at not above this temperature until after separation of the undissolved or precipitated components. For example, dissolution may be effected at ordinary temperature followed by decantation or filtration either at ordinary temperature or after chilling to below room temperature as for example to at least about -10 C.

The process of the present invention is applicable to the purification of any type of dark-colored rosin including the total resinous extract of pine wood obtained by extraction with such solvents as benzene and toluene, the resionus extract known as FF rosin obtained by extracting pine wood with hot petroleum distillate such as gasoline, and generally impure rosins having a color below E on the U. S. standard color grade scale for rosin types.

As used herein, the term FF rosin in accordance with conventional usage designates impure rosin containing color bodies and which has not been subjected to refining to eliminate the color bodies. FF rosin grades lower than E on the U. Sastandard scale for rosin types.

Below are given several specific examples showing the method of carrying the present invention in certain of these examples had a boiling range of from about 60 C. to about 70 C., had an aniline point of 64.8" C., and analyzed as follows:

Per cent Unsaturates Nil Aromatics 2.7 Naphthenes 10 Parafiins (at least 90% hexanes) 87 Example 1 One hundred grams of the crude resinous extract consisting of the residue remaining from distillation of a benzene extract of pine Wood (Southern long leaf pine) to remove the benzene and volatile terpene oils, and 900 g. of commer- Example 2 Three hundred grams of the crude resinous extract used in Example 1 and 2700 g. of commer cial hexane were agitated to solution at room temperature in three separate lots each of which was then chilled to 10 C. and held at this temperature for minutes. These lots were then filtered at this temperature. The filtrates were combined and evaporated to yield 203.3 g. of rosin grading 40 Amber-P75 Red ora G grade.

The commercial hexane employed Example 3 Fifty grains of the crude resinous extract used in Example 1 and 450 g. commercial hexane were refluxed for 60 minutes. The solution was then cooled at room temperature, settled, and the clear supernatant solution decanted from the insoluble material and evaporated to give 33.3 g. of an H colored rosin.

Example 4 This example was conducted in exactly the same manner as Example 3 except that the hot solution was cooled to 10 C. before decanting the soluble fraction. The rosin recovered from the clear solution had a color of I.

Example 5 Two hundred grams of FF Wood rosin was shaken at room temperature with 1800 g. of petroleum ether having a boiling range of 40 C. to 90 'C. and which was substantially saturated and substantially free from aromatic hydrocarbons, until all the soluble portion of the rosin was dissolved. The solution was then 'poured'ofi and evaporated to recover the rosin which was a good F grade, the intense red color being almost entirely absent. The insoluble residue was very dark red in color and of a B grade. 1

Example 6 Two hundredg. of FF wood rosin was added to 1000 grams of substantially saturated, substantially aromatic-free, low boiling gasoline having a specific gravity of 0.641 at 15 C. .and the following distillation analysis:

Percent First drop at 28 C Over at 40 C ,29

109 2.31/ .Residue .4

The mixture was refluxed for 1 .hour and then allowed to cool whereupon the clear rosin solution was decanted from the residue, and the gasoline removed from the clear solution by steam distillation, yielding a rosin of a good F grade and from which the reddish color had been completely removed.

Example 7 present invention offers .a simple and economical method of purifying dark-colored rosin. ".The

process is an effective and economical .preliminary to the further refining of the rosin by-a.se-

lective refining agent such .as a selective solvent,

such as furfural, aniline, ethylene chlorohydrin, aqueous phenol, and the like, in the mannenset forth for example in Kaiser and Hancock? Patent No. 1,715,085 ora-selectivewadsorbentsuch as fullers earth, activated clay, activated carbon, and the like, to a very pale or Water-white grade. In this way, the total costs of obtaining from pine Wood rosin of a given pale grade is materially reduced. Numerous other advantages of the process of the present invention will be apparent to those skilled in the art.

This application is a continuation-in-part of my prior and copending application, Serial No. 264,970, filed March 30, 1939.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

What I claim and desire to protect by Letters Patent is:

1. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by Weight of impure rosin in from about 1 to about parts by Weight of a normally liquid readily evaporated petroleum hydrocarbon solvent comprising a preponderance of hexane, said solvent containing in excess of 50% hexane and being sufficiently free of aromatic, unsaturated and naphthenic constituents to have an aniline point above 60 C., separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

2. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by weight of impure rosin in from about 1 to about 10 parts by Weight of a normally liquid readily evaporated petroleum hydrocarbon solvent comprising at least 90% by.

weight of hexane, said solvent containing less than 3% aromatic and less than 3% unsaturated constituents, separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

3. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by weight of impure rosin in from about 1 to about 10 parts by weight of a substantially saturated petroleum ether containing at least 50% hexane and substantially free from aromatic compounds, said solvent having an aniline point of above 60 C. separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

4. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by weight of impure rosin in from about 1 to about 10 parts by Weight of a normally liquid readily evaporated petroleum hydrocarbon solvent, said solvent having an aniline point above 60 C. and containing at least 50% hexane, less than 3% of unsaturated hydrocarbons, less than 3% of aromatic hydrocarbons, less than of naphthene hydrocarbons, and not over 15% of unsaturates, aromatics and naphthenes, separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

5. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by weight of impure rosin in about nine parts by weight of commercial hexane having an aniline point above 60 C., containing less than 3% of unsaturated hydrocarbons, less than 3% of aromatic hydrocarbons, less than 15% of naphthene hydrocarbons, and not over 15% of usaturates, aromatics and naphthenes, said hexane boiling between about 60 C. and about C., separating undissolved constituents from the solution, and evaporating the hexane from the solution to recover the dissolved rosin.

6. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating at at least room temperature one part by weight of impure rosin in from about 1 to about 10 parts by Weight of a substantially saturated normally liquid readily evaporated petroleum hydrocarbon solvent containing at least 50% hexane and substantially free from aromatic hydrocarbons and having an aniline point above 60 C., chilling the mixture to substantially below room temperature, separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

7. The method of producing light-colored rosin from crude, dark-colored rosin which consists in treating one part by Weight of impure rosin in from about 1 to about 10 parts by weight of a normally liquid substantially saturated petroleum hydrocarbon solvent boiling substantially within the range of from about 33 C. to about C., said solvent being substantially free from aromatic and unsaturated hydrocarbons and having an aniline point above 60 C., separating undissolved constituents from the solution, and evaporating the solvent from the solution to recover the dissolved rosin.

8. In the process of decolorizing and refining dark-colored, impure wood rosin, the steps which comprise treating the rosing with a petroleum distillate consisting essentially of hexane having a boiling point range of substantially about 60 C. to about 70 C. and an aniline point of above 60 C. and separating undissolved constituents from the solution.

9. In the process of decolorizing and refining dark-colored, impure wood rosin, the steps which comprise treating the rosin with a substantially saturated petroleum hydrocarbon solvent which is substantially free from aromatic hydrocarbons and which has a boiling point range of from substantially 60 C. to about '7 0 C. and an aniline point of above 60 C., and separating the undissolved constituents from the solution.

10. The process of decolorizing and refining dark-colored, impure wood rosin which comprises treating the rosin with a petroleum distillate consisting essentially of hexane having a boiling point range from about 60 C. to about 70 C., heating the solution to refluxing temperature, cooling the solution to at least about -l0 C., thereby causing a separation of undissolved constituents from the rosin solution, removing said undissolved constituents from the solution, then recovering the rosin from the solution by eliminating the petroleum solvent therefrom.

ROBERT W. MARTIN. 

